BATH, Maine — Federal labor officials have sued a Bath dentist for allegedly retaliating against two dental hygienists who alerted authorities to unsanitary conditions at her practice.

The suit filed Friday in U.S. District Court in Portland by the U.S. Labor Department alleges that Tammy Cook, owner of Bath Family Dental, discriminated against Dorothy Shafran and Chelsea Huntington for complaining about what the hygienists believed to be lapses in infection control at the office.

Cook’s attorney, Robert Kline, denied the allegations and said Cook operates a clean and safe dental practice.

The suit seeks lost wages, benefits, and compensatory and punitive damages for Huntington and Shafran.

The hygienists filed complaints with the Occupational Safety and Health Administration in October 2011 after alerting Cook to health and safety hazards at the office, according to the complaint. Shafran and Huntington complained that patient rooms weren’t properly cleaned and personnel failed to wash their hands before treatment and didn’t wear gloves.

The hygienists said Cook failed to address their concerns.

The Labor Department alleged in the lawsuit that during a subsequent surprise inspection at the practice, Cook told OSHA officials that she knew who had filed the complaint and threatened to fire them. The inspectors informed Cook that whistleblowers are protected under federal law, and Cook replied that she would fire the complainants for another reason and OSHA would not be able to prove otherwise, according to the complaint.

Working conditions worsened for both women, including retaliatory disciplinary warnings from Cook, the complaint alleges. Shafran was fired and Huntington resigned on the same day after Cook told her she would be demoted.

The disciplinary actions resulted from multiple rule violations by the two hygienists, Kline said. He provided a copy of a decision by the Maine Department of Labor related to Shafran’s claim for unemployment benefits that found Cook proved Shafran acted irresponsibly and her misconduct put the dental practice in jeopardy.

Shafran’s misconduct included failing to wear safety glasses while working on patients and failing to provide documentation of being vaccinated against hepatitis B, according to the decision.

OSHA found no lack of infection control at the practice, Kline said. He provided a copy of an Oct. 20, 2011, OSHA citation that shows no enforcement action was taken related to Huntington’s original health and safety complaints.

“There’s not anything that suggests Dr. Cook’s hygiene practices are not appropriate or consistent with OSHA regulations,” he said.

The citation noted several paperwork violations and a $3,000 fine involving the practice’s plan for handling blood-borne pathogens, which was incomplete.

Cook, a former dental hygienist, purchased the small practice in 2007, Kline said. She was licensed to practice as a dentist in Maine in 2005.